1. Technical Field
The present invention relates to a technique which reduces a display defect in a liquid crystal display panel.
2. Related Art
A liquid crystal display panel has a configuration in which pixel electrodes corresponding to pixels are arranged in a matrix shape on one of a pair of substrates and a common electrode is installed on the other thereof to be common over the respective pixels, and liquid crystal is interposed between the pixel electrodes and the common electrode. In such a configuration, if voltage according to a gray scale level is applied and held between the pixel electrodes and the common electrode, an orientation state of the liquid crystal is regulated for each pixel, and thus transmittance or reflectance is controlled. Thus, in this configuration, only a component in a direction from the pixel electrodes to the common electrode (or in a reverse direction), that is, in a direction perpendicular to a substrate surface (longitudinal direction), within an electric field acting on liquid crystal molecules, contributes to a display control.
However, in recent years as pixel pitch has become narrow for the purpose of miniaturization and high precision, an electric field has been generated between adjacent pixel electrodes, that is, in a direction parallel to a substrate surface (transverse direction), the affect of which cannot be neglected. For example, if a transverse electric field is applied to liquid crystal which is driven by a longitudinal electric field, such as a VA (Vertical Alignment) method or a TN (Twisted Nematic) method, an orientation error of the liquid crystal (reverse tilt domain) occurs, thereby causing a display defect.
In order to reduce the effect of the reverse tilt domain, there is for example proposed a technique of contriving a structure of a liquid crystal display panel, for example, by regulating the shape of a light blocking layer (opening section) over pixel electrodes (refer to JP-A-6-34965 (FIG. 1), for example), or a technique which determines that the reverse tilt domain occurs in a case where an average luminance value calculated from a video signal is equal to or smaller than a threshold and clips a video signal which is equal to or larger than a preset value (refer to JP-A-2009-69608 (FIG. 2), for example).
However, in the technique of reducing the reverse tilt domain by means of the structure of the liquid crystal display panel, the aperture ratio is easily decreased. Further, it is difficult to apply the technique to an existing liquid crystal display panel without contrivance of the structure. On the other hand, in the technique which clips the video signal which is equal to or larger than the preset value, the brightness of a displayed image is indiscriminately limited to the preset value.